Pen-type injector

ABSTRACT

The present invention relates to injectors, such as pen-type injectors, that provide for administration of medicinal products from a multidose-cartridge and permit a user to set the delivery dose. The injector may include a housing, a piston rod adapted to operate through the housing, a dose dial sleeve located between the housing and the piston rod, and a drive sleeve located between the dose dial sleeve and the piston rod. The dose dial sleeve may have a helical thread of first lead and the drive sleeve may have a helical groove of second lead. The first lead of the helical thread and the second lead of the helical groove may be the same.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 11/483,546, filed Jul. 11, 2006, which is a continuation ofU.S. patent application Ser. No. 10/790,225, filed Mar. 2, 2004, whichclaims priority to GB 0304822.0 filed Mar. 3, 2003, the entire contentsof which are incorporated herein by reference.

BACKGROUND

The present invention relates to pen-type injectors, that is, toinjectors of the kind that provide for administration by injection ofmedicinal products from a multidose cartridge. In particular, thepresent invention relates to such injectors where a user may set thedose.

Such injectors have application where regular injection by personswithout formal medical training occurs. This is increasingly commonamongst those having diabetes where self-treatment enables such personsto conduct effective management of their diabetes.

These circumstances set a number of requirements for pen-type injectorsof this kind. The injector must be robust in construction, yet easy touse both in terms of the manipulation of the parts and understanding bya user of its operation. In the case of those with diabetes, many userswill be physically infirm and may also have impaired vision. Where theinjector is to be disposable rather than reusable, the injector shouldbe cheap to manufacture and easy to dispose of (preferably beingsuitable for recycling).

SUMMARY

It is an advantage of the present invention that an improved pen-typeinjector is provided.

According to a first aspect of the present invention, a pen-typeinjector comprises

a housing;

a piston rod adapted to operate through housing;

a dose dial sleeve located between the housing and the piston rod, thedose dial sleeve having a helical thread of first lead;

a drive sleeve located between the dose dial sleeve and the piston rod,the drive sleeve having a helical groove of second lead;

characterized in that the first lead of the helical thread and thesecond lead of the helical groove are the same.

Preferably, the piston rod has a first threaded portion at a first endand a second threaded portion at a second end;

an insert or radially inwardly extending flange is located in thehousing and through which the first threaded portion of the piston rodmay rotate;

the dose dial sleeve being rotatable with respect to the housing and theinsert;

-   -   the drive sleeve being releasably connected to the dose dial        sleeve and connected to the piston rod for rotation with respect        thereto along the second threaded portion of the piston rod;

a button is located on the dose dial sleeve and rotatable with respectto the does dial sleeve; and

-   -   clutch means are provided which upon depression of the button        permit rotation between the dose dial sleeve and the drive        sleeve.

Preferably, the injector further comprises a nut which is rotatable withrespect to the drive sleeve and axially displaceable but not rotatablewith respect to the housing.

More preferably, the drive sleeve is provided at a first end with firstand second flanges with an intermediate thread between the first andsecond flanges, the nut being disposed between the first and secondflanges and keyed to the housing by spline means. Additionally, a firstradial stop may be provided on a second face of the nut and a secondradial stop may be provided on a first face of the second flange.

Preferably, the first thread of the piston rod is oppositely disposed tothe second thread of the piston rod.

Preferably, a second end of the clutch is provided with a plurality ofdog teeth adapted to engage with a second end of the dose dial sleeve.

Preferably, the pen-type injector further includes clicker meansdisposed between the clutch means and spline means provided on thehousing.

More preferably, the clicker means comprises a sleeve provided at afirst end with a helically extending arm, a free end of the arm having atoothed member, and at a second end with a plurality ofcircumferentially directed saw teeth adapted to engage a correspondingplurality of circumferentially saw teeth provided on the clutch means.

Alternatively, the clicker means comprises a sleeve provided at a firstend with at least one helically extending arm and at least one springmember, a free end of the arm having a toothed member, and at a secondend with a plurality of circumferentially directed saw teeth adapted toengage a corresponding plurality of circumferentially directed saw teethprovided on the clutch means.

Preferably, the main housing is provided with a plurality of maximumdose stops adapted to be abutted by a radial stop provided on the dosedial sleeve. More preferably, at least one of the maximum dose stopscomprises a radial stop located between a helical rib and spline meansprovided at a second end of the housing. Alternatively, at least one ofthe maximum dose stops comprises a part of a raised window portionprovided at a second end of the housing.

Preferably, the dose dial sleeve is provided with a plurality ofradially extending members adapted to abut a corresponding plurality ofradial stops provided at a second end of the housing.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be described with reference to the accompanyingdrawings in which:

FIG. 1 shows a sectional view of a pen-type injector in accordance withthe present invention in a first, cartridge full, position;

FIG. 2 shows a sectional view of the pen-type injector of FIG. 1 in asecond, maximum first dose dialed, position;

FIG. 3 shows a sectional view of the pen-type injector of FIG. 1 in athird, first maximum first dose dispensed, position;

FIG. 4 shows a sectional view of the pen-type injector of FIG. 1 in afourth, final dose dialed, position;

FIG. 5 shows a sectional view of the pen-type injector of FIG. 1 in afifth, final dose dispensed, position;

FIG. 6 shows a cut-away view of a first detail of the pen-type injectorof FIG. 1;

FIG. 7 shows a partially cut-away view of a second detail of thepen-type injector of FIG. 1;

FIG. 8 shows a partially cut-away view of a third detail of the pen-typeinjector of FIG. 1;

FIG. 9 shows the relative movement of parts of the pen-type injectorshown in FIG. 1 during dialing up of a dose;

FIG. 10 shows the relative movement of parts of the pen-type injectorshown in FIG. 1 during dialing down of a dose;

FIG. 11 shows the relative movement of parts of the pen-type injectorshown in FIG. 1 during dispensing of a dose;

FIG. 12 shows a partially cut-away view of the pen-type injector of FIG.1 in the second, maximum first dose dialed, position;

FIG. 13 shows a partially cut-away view of the pen-type injector of FIG.1 in the fourth, final dose dialed, position;

FIG. 14 shows a partially cut-away view of the pen-type injector of FIG.1 in one of the first, third or fifth positions;

FIG. 15 shows a cut-away view of a first part of a main housing of thepen-type injector of FIG. 1; and

FIG. 16 shows a cut-away view of a second part of the main housing ofthe pen-type injector of FIG. 1.

DETAILED DESCRIPTION

Referring first to FIGS. 1 to 5, there may be seen a pen-type injectorin accordance with the present invention in a number of positions.

The pen-type injector comprises a housing having a first cartridgeretaining part 2, and second main housing part 4. A first end of thecartridge retaining means 2 and a second end of the main housing 4 aresecured together by retaining features 6. In the illustrated embodiment,the cartridge retaining means 2 is secured within the second end of themain housing 4.

A cartridge 8 from which a number of doses of medicinal product may bedispensed is provided in the cartridge retaining part 2. A piston 10 isretained in a first end of the cartridge 8.

A removable cap 12 is releasably retained over a second end of thecartridge retaining part 2. In use the removable cap 12 can be replacedby a user with a suitable needle unit (not shown). A replaceable cap 14is used to cover the cartridge retaining part 2 extending from the mainhousing 4. Preferably, the outer dimensions of the replaceable cap 14are similar or identical to the outer dimensions of the main housing 4to provide the impression of a unitary whole when the replaceable cap 14is in position covering the cartridge retaining part 2.

In the illustrated embodiment, an insert 16 is provided at a first endof the main housing 4. The insert 16 is secured against rotational orlongitudinal motion. The insert 16 is provided with a threaded circularopening 18 extending therethrough. Alternatively, the insert may beformed integrally with the main housing 4 the form of a radiallyinwardly directed flange having an internal thread.

A first thread 19 extends from a first end of a piston rod 20. Thepiston rod 20 is of generally circular section. The first end of thepiston rod 20 extends through the threaded opening 18 in the insert 16.A pressure foot 22 is located at the first end of the piston rod 20. Thepressure foot 22 is disposed to abut a second end of the cartridgepiston 10. A second thread 24 extends from a second end of the pistonrod 20. In the illustrated embodiment the second thread 24 comprises aseries of part threads rather than a complete thread. The illustratedembodiment is easier to manufacture and helps reduce the overall forcerequired for a user to cause medicinal product to be dispensed.

The first thread 19 and the second thread 24 are oppositely disposed.The second end of the piston rod 20 is provided with a receiving recess26.

A drive sleeve 30 extends about the piston rod 20. The drive sleeve 30is generally cylindrical. The drive sleeve 30 is provided at a first endwith a first radially extending flange 32. A second radially extendingflange 34 is provided spaced a distance along the drive sleeve 30 fromthe first flange 32. An intermediate thread 36 is provided on an outerpart of the drive sleeve 30 extending between the first flange 32 andthe second flange 34. A helical groove 38 extends along the internalsurface of the drive sleeve 30. The second thread 24 of the piston rod20 is adapted to work within the helical groove 38.

A first end of the first flange 32 is adapted to conform to a secondside of the insert 16.

A nut 40 is located between the drive sleeve 30 and the main housing 2,disposed between the first flange 32 and the second flange 34. In theillustrated embodiment the nut 40 is a half-nut. This assists in theassembly of the injector. The nut 40 has an internal thread matching theintermediate thread 36. The outer surface of the nut 40 and an internalsurface of the main housing 4 are keyed together by splines 42 (seeFIGS. 10, 11, 15 and 16) to prevent relative rotation between the nut 40and the main housing 4, while allowing relative longitudinal movementtherebetween.

A shoulder 37 is formed between a second end of the drive sleeve 30 andan extension 38 provided at the second end of the drive sleeve 30. Theextension 38 has reduced inner and outer diameters in comparison to theremainder of the drive sleeve 30. A second end of the extension 38 isprovided with a radially outwardly directed flange 39.

A clicker 50 and a clutch 60 are disposed about the drive sleeve 30,between the drive sleeve 30 and a dose dial sleeve 70 (to be describedbelow).

The clicker 50 is located adjacent the second flange 34 of the drivesleeve 30. The clicker 50 is generally cylindrical and is provided at afirst end with a flexible helically extending arm 52 (shown most clearlyin FIG. 6). A free end of the arm 52 is provided with a radiallydirected toothed member 54. A second end of the clicker 50 is providedwith a series of circumferentially directed saw teeth 56 (of FIG. 7).Each saw tooth comprises a longitudinally directed surface and aninclined surface.

In an alternative embodiment (not shown) the clicker means furtherincludes at least one spring member. The at least one spring memberassists in the resetting of the clutch means 60 following dispense.

The clutch means 60 is located adjacent the second end of the drivesleeve 30. The clutch means 60 is generally cylindrical and is providedat a first end with a series of circumferentially directed saw teeth 66(see FIG. 7). Each saw tooth comprises a longitudinally directed surfaceand an inclined surface. Towards the second end 64 of the clutch means60 there is located a radially inwardly directed flange 62. The flange62 of the clutch means 60 is disposed between the shoulder 37 of thedrive sleeve 30 and the radially outwardly directed flange 39 of theextension 38. The second end of the clutch means 60 is provided with aplurality of dog teeth 65 (FIG. 8). The clutch 60 is keyed to the drivesleeve 30 by way of splines (not shown) to prevent relative rotationbetween the clutch 60 and the drive sleeve 30.

In the illustrated embodiment, the clicker 50 and the clutch 60 eachextend approximately half the length of the drive sleeve 30. However, itwill be understood that other arrangements regarding the relativelengths of these parts are possible.

The clicker 50 and the clutch means 60 are normally engaged, that is asshown in FIG. 7.

A dose dial sleeve 70 is provided outside of the clicker 50 and clutchmeans 60 and radially inward of the main housing 4. A helical groove 74is provided about an outer surface of the dose dial sleeve 70.

The main housing 4 is provided with a window 44 through which a part ofthe outer surface of the dose dial sleeve may be seen. The main housing4 is further provided with a helical rib 46, adapted to be seated in thehelical groove 74 on the outer surface of the dose dial sleeve 70. Thehelical rib 46 extends for a single sweep of the inner surface of themain housing 4. A first stop 100 is provided between the splines 42 andthe helical rib 46 (FIG. 15). A second stop 102, disposed at an angle of180° to the first stop 100 is formed by a frame surrounding the window44 in the main housing 4 (FIG. 16).

Conveniently, a visual indication of the dose that may be dialed, forexample reference numerals (not shown). is provided on the outer surfaceof the dose dial sleeve 70. The Window 44 conveniently only allows to beviewed a visual indication of the dose currently dialed.

A second end of the dose dial sleeve 70 is provided with an inwardlydirected flange in the form of number of radially extending members 75.A dose dial grip 76 is disposed about an outer surface of the second endof the dose dial sleeve 70. An outer diameter of the dose dial grip 76preferably corresponds to the outer diameter of the main housing 4. Thedose dial grip 76 is secured to the dose dial sleeve 70 to preventrelative movement therebetween. The dose dial grip 76 is provided with acentral opening 78. An annular recess 80 located in the second end ofthe dose dial grip 76 extends around the opening 78.

A button 82 of generally ‘T’ section is provided at a second end of thepen-type injector. A stem 84 of the button 82 may extend through theopening 78 in the dose dial grip 76, through the inner diameter of theextension 38 of the drive sleeve 30 and into the receiving recess 26 ofthe piston rod 20. The stem 84 is retained for limited axial movement inthe drive sleeve 30 and against rotation with respect thereto. A head 85of the button 82 is generally circular. A skirt 86 depends from aperiphery of the head 85. The skirt 86 is adapted to be seated in theannular recess 80 of the dose dial grip 76.

Operation of the pen-type injector in accordance with the presentinvention will now be described. In FIGS. 9, 10 and 11 arrows A, B. C,D, E, F and G represent the respective movements of the button 82, thedose dial grip 76, the dose dial sleeve 70, the drive sleeve 30, theclutch means 60, the clicker 50 and the nut 40.

To dial a dose (FIG. 9) a user rotates the dose dial grip 76 (arrow A).With the clicker 50 and clutch means 60 engaged, the drive sleeve 30,the clicker 50, the clutch means 60 and the dose dial sleeve 70 rotatewith the dose dial grip 76.

Audible and tactile feedback of the dose being dialed is provided by theclicker 50 and the clutch means 60. Torque is transmitted through thesaw teeth 56, 66 between the clicker 50 and the clutch means 60. Theflexible arm 52 deforms and drags the toothed member 54 over the splines42 to produce a click. Preferably, the splines 42 are dispose such thateach click corresponds to a unit dose.

The helical groove 74 on the dose dial sleeve 70 and the helical groove38 in the drive sleeve 30 have the same lead. This allows the dose dialsleeve 70 (arrow C) to extend from the main housing 4 and the drivesleeve 30 (arrow D) to climb the piston rod 20 at the same rate. At thelimit of travel, a radial stop 104 on the dose dial sleeve 70 engageseither the first stop 100 or the second stop 102 provided on the mainhousing 4 to prevent further movement. Rotation of the piston rod 20 isprevented due to the opposing directions of the overhauled and driventhreads on the piston rod 20.

The nut 40, keyed to the main housing 4, is advanced along theintermediate thread 36 by the rotation of the drive sleeve 30 (arrow D).When the final dose dispensed position (FIGS. 4, 5 and 13) is reached, aradial stop 106 formed on a second surface of the nut 40 abuts a radialstop 108 on a first surface of the second flange 34 of the drive sleeve30 preventing both the nut 40 and the drive sleeve 30 from rotatingfurther.

In an alternative embodiment (not shown) a first surface of the nut 40is provided with a radial stop for abutment with a radial stop providedon a second surface of the first flange 32. This aids location of thenut 40 at the cartridge full position during assembly of the pen-typeinjector.

Should a user inadvertently dial beyond the desired dosage, the pen-typeinjector allows the dosage to be dialed down without dispense ofmedicinal product from the cartridge (FIG. 10). The dose dial grip 76 iscounter rotated. This causes the system to act in reverse. The flexiblearm 52 now acts as a ratchet preventing the clicker from rotating. Thetorque transmitted through the clutch means 60 causes the saw teeth56,66 to ride over one another to create the clicks corresponding todialed dose reduction. Preferably the saw teeth 56,66 are so disposedthat the circumferential extent of each saw tooth corresponds to a unitdose.

When the desired dose has been dialed, the user may then dispense thisdose by depressing the button 82 (FIG. 11). This displaces the clutchmeans 60 axially with respect to the dose dial sleeve 70 causing the dogteeth 65 to disengage. However the clutch means 60 remains keyed inrotation to the drive sleeve 30. The dose dial sleeve 70 and associateddose dial grip 76 are now free to rotate (guided by the helical rib 46located in helical groove 74).

The axial movement deforms the flexible arm 52 of the clicker 50 toensure the saw teeth 56,66 cannot be overhauled during dispense. Thisprevents the drive sleeve 30 from rotating with respect to the mainhousing 4 though it is still free to move axially with respect thereto.This deformation is subsequently used to urge the clicker 50, and theclutch 60, back along the drive sleeve 30 to restore the connectionbetween the clutch 60 and the dose dial sleeve 70 when pressure isremoved from the button 82.

The longitudinal axial movement of the drive sleeve 30 causes the pistonrod 20 to rotate though the opening 18 in the insert 16, thereby toadvance the piston 10 in the cartridge 8. Once the dialed dose has beendispensed, the dose dial sleeve 70 is prevented from further rotation bycontact of a plurality of members 110 (FIG. 14) extending from the dosedial grip 76 with a corresponding plurality of stops 112 formed in themain housing 4 (FIGS. 15 and 16). In the illustrated embodiment, themembers 110 extend axially from the dose dial grip 76 and have aninclined end surface. The zero dose position is determined by theabutment of one of the axially extending edges of the members 110 with acorresponding stop 112.

1. A dispensed dose indicator mechanism for a pen-type injector,comprising: a housing having an internal surface with one or moresplines; a drive sleeve configured to move both axially and rotationallyrelative to the internal surface of the housing, the drive sleeve havingan outer surface on which a thread is disposed; and a nut engaged withthe thread, where the nut is fixed rotationally with respect to thehousing and is axially displaceable along the thread when the drivesleeve is rotated.
 2. The dispensed dose indicator mechanism of claim 1further characterized in that the outer surface of the drive sleeve hasa first radially extending flange and a second radially extendingflange, the thread is disposed between the two flanges.
 3. The dispenseddose indicator mechanism of claim 1 where the nut is keyed to the one ormore splines on the internal surface of the housing to prevent the nutfrom rotating relative to the housing while allowing axial movementrelative to the housing.
 4. The dispensed dose indicator mechanism ofclaim 1 where the nut is a half nut.
 5. The dispensed dose indicatormechanism of claim 1 where axially displacement of the nut is indicativeof dispensed doses.
 6. The dispensed dose indicator mechanism of claim 1where the thread is proportional to available doses of medicamentcontained in a cartridge attached to the pen-type injector.
 7. Thedispensed dose indicator mechanism of claim 1 where a first radial stopon the nut engages a second radial stop on the second flange when afinal dose of medicament is dispensed from a cartridge attached to thepen-type injector.
 8. The dispensed dose indicator mechanism of claim 1where a radial stop on the nut engages a radial stop on the first flangeindicative of a cartridge full position.
 9. A method of determining afinal dose of a medicament contained in a cartridge in a pen-typeinjector comprising, providing a housing containing a drive sleevehaving a nut threadedly engaged to an outer surface of the drive sleevebetween a first and second flange; configuring the nut and thread to beindicative of dispensed doses; and configuring the second flange toengage the nut when a final dose of medicament is dispensed from acartridge attached to the pen-type injector.
 10. The method of claim 9further comprising configuring the nut and second flange to prevent thedrive sleeve from rotating when the final dose of medicament isdispensed.